The role of T cells expressing specific V beta elements was examined in the regulation of allergen-specific immunoglobulin (Ig)E production and airways responsiveness (AR). In BALB/c mice, inhalation of the allergen ovalbumin (OVA) induced an IgE anti-OVA response, immediate cutaneous reactivity, and increased AR. These results were associated with an expansion of V beta 8.1/8.2 T cells in local draining lymph nodes of the airways and the lung. Transfer of V beta 8.1/8.2 T cells from sensitized mice stimulated an IgE anti-OVA response, immediate cutaneous hypersensitivity, and increased AR in naive syngeneic recipients. In contrast, OVA-reactive V beta 2 T cells inhibited these effects. These data demonstrate for the first time that T cells with different V beta specificities play a critical role in the in vivo regulation of allergen-specific IgE production and AR.